CONVERSION OF DYNORPHIN-A(1-8) TO [LEU5]-ENKEPHALIN IN RAT CENTRAL NERVOUS-TISSUE DURING DEVELOPMENT

Rat central nervous tissue contains enzymic activity that is able to c onvert the kappa-receptor preferring opioid peptide dynorphin A(1-8) t o the delta-mu-receptor preferring opioid peptide [Leu5]enkephalin. Th e ontogeny of this conversion process has been studied in vitro using cortex, striatum, cerebellum and spinal cord tissues of the developing rat brain. Evidence for the enzymic cleavage of the Leu5-Arg6 bond of dynorphin A(1-8) to afford [Leu5]enkephalin was observed as early as neonatal day 1. The degree of conversion increased up to day 7, at whi ch time adult levels were attained. Results in all tissues studied wer e similar. The relationship between the increase in the conversion pro cess with age and the ontogeny of opioid peptides and their receptors may indicate an important role for the process in the developing nervo us system.